Note: Descriptions are shown in the official language in which they were submitted.
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1
COMBINATION CONDUCTION/CONVECTION FURNACE
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of foundry processing,
and more particularly to heat treating metal castings and reclaiming sand from
sand cores and sand molds used in the manufacture of metal castings.
Many changes have been made in the field of heat treating of metal
castings and reclaiming sand from sand cores and sand molds used in the
manufacture of metal castings. Examples of some recent disclosures which
address the heat treating of castings, removal of sand cores, and further
reclaiming
of sand are found in U.S. Pat. Nos. 5,294,094, 5,354,038, 5,423,370, and
5,829,509 (hereinafter sometimes referred to collectively as the "Reference
Patents"), each of which is expressly incorporated herein by reference, in
their
entirety. Those patents disclose a three-in-one process/integrated system that
(i)
receives and heat treats a casting, (ii) removes sand core/sand mold materials
from the casting, and (iii) reclaims sand from the sand core/sand mold
materials
removed from the casting; the'094 and'038 patents embodying a convection
furnace species, the'370 patent embodying a conduction furnace species, and
the
'509 patent alternately embodying either a conduction furnace species or a
convection furnace species (and adding an integrated cooling chamber). The
sand
core/sand mold materials (referred to hereafter as sand core materials)
comprise
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sand that is held together by a binder material such as, but not limited to, a
combustible organic resin binder.
Technology such as that disclosed in the above-mentioned patents are
driven, for example, by: competition; increasing costs of raw materials,
energy,
labor, and waste disposal; and environmental regulations. Those factors
continue
to mandate improvements in the field of heat treating and sand reclamation.
SUMMARY OF THE INVENTION
Briefly described, the present invention provides a single furnace system
io which integrates, in combination, a plurality of distinct heating
environments
(which in the preferred embodiments include two heating environments
comprising a conduction heating environment and a convection heating
environment) integrated such that the plurality of environments define a
continuous heating chamber through which a moving workpiece (such as a
casting) transitions from one heating environment to the other without being
exposed to the atmosphere. In accordance with the preferred methods, the
transitioning of the casting from one environment to the other is accomplished
with no meaningful change in temperature.
In accordance with a second aspect of the invention, improved species
embodiments of a 3-in-I processing system of the genus described in the above
identified prior patent specifications are provided. These species embodiments
of
the present invention disclose a system apparatus and method for processing a
casting which perform the integrated processes of core removal, sand
reclaiming
and heat treatment in a combination conduction and convection furnace system.
Other objects, features, and advantages of the present invention will
become apparent upon reading and understanding this specification, taken in
conjunction with the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic, side cut-away view of a combination
conduction/convection furnace, in accordance with the preferred embodiment of
the present invention.
Fig. lA is an isolated view of hoist and rail components of one
embodiment of a transport system utilized in the furnace of the present
invention.
Fig. 2 is a schematic, side cut-away view of a combination
conduction/convection furnace, in accordance with an alternate embodiment of
the present invention.
Fig. 3 is a schematic, side cut-away view of a combination
conduction/convection furnace, in accordance with a second alternate
embodiment of the present invention.
Fig. 4-6 are schematic, side cut-away views of alternate embodiments of
multiple heating environments comprising an integrated continuous heating
chamber of a furnace system in accordance with the present invention.
Fig. 7 is a schematic side cut away view of an alternate embodiment of the
convection heating segment including a casting rotary mechanism.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to the drawings in which like numerals represent like
components throughout the several views, Fig. I depicts in schematic
representation a combination conduction/convection furnace 10 in accordance
with a preferred embodiment of the present invention. The combination furnace
10 is seen as comprising a frame structure 12 which defines an enclosed
heating
chamber 14 and includes insulated walls 15 surrounding the heating chamber, an
entrance portal 16 outfitted with a selectively closable insulated inlet door
17 and
an exit portal 18 outfitted with a selectively closable insulated outlet door
19. The
heating chamber 14 is seen as divided into two major heating chamber segments
23, 24 which together comprise the continuous heating chamber 14 and are
interconnected by a transitional passage 25. In accordance with the preferred
embodiments of the present invention, the transitional passage 25 is of
sufficient
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size and orientation to allow for the easy movement from the first heating
chamber segment 23 to the second heating chamber segment 24 of a work piece,
such as a casting, as well as the free movement of heat, gases, dust, and the
like
from one chamber segment to the other chamber segment. An integrated
transportation system 26 transports the castings from the entrance portal 16,
through the first heating chamber 23, into and through the second heating
chamber 24, to the exit portal 18.
In accordance with the preferred embodiments of the present invention,
each of the first heating chamber segment 23 and second heating chamber
segment 24 is equipped to heat a casting within the respective chamber segment
by a furnace heating process which is of a process distinct from the furnace
heating process with which the other chamber segment is equipped.
The herein depicted, preferred embodiments of Figs. 1-3 are equipped
with a conduction furnace heating process, in the form of a fluidized bed
furnace,
in the first heating chamber segment 23 and are equipped with a convection
type
heating furnace in the second heating chamber segment 24. The heating
environment provided in the first heating chamber segment 23 is, thus, an
environment as is created by a conduction type furnace (such as a fluidized
bed
furnace) and the heating environment of the second heating chamber segment 24
is, thus, an environment as is created by a convection type furnace. As
depicted
in the drawings, a bed 27 of particles (the fluidizing medium) mostly fills
the first
heating chamber segment 23, and conduit 28 for the introduction of fluidizing
gases are provided. A heating source (not shown) provides heated fluidizing
gases to the conduit 28. In this heating chamber segment 23, castings are
immersed within the fluidized bed 27 where heat is transferred to the castings
from surrounding heated bed particles by conduction, and where the castings
are
heated to an appropriate temperature for an appropriate period of time to
accomplish one or more (full or partial) desired casting processing steps (an
example of which is expressed below). The convection heating chamber segment
24 includes heating sources (not shown) which heat the air inside the heating
chamber segment such that the heat transfers by convection to a casting
contained
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within the convection heating chamber segment and such that the castings are
heated to an appropriate temperature for an appropriate period of time to
accomplish one or more (full or partial) desired casting processing steps (an
example of which is expressed below).
Referring again, generally, to Fig. 1(and Figs. 2 and 3), the combination
ftunace 10 is seen as also including a loading station 40 outside the furnace
structure 12 and, an entry zone 41 inside the furnace structure 12. The entry
zone
41, of the herein depicted embodiments of Figs. 1 and 2, occupies a portion of
the
heating chamber 14 positioned above the fluidized bed segment 23 and receives
1o rising heat, thus exposing castings in the entry zone to initial chamber
heat. The
integrated transport system 26, of the herein depicted embodiments is
comprised
of a combination of a charge transport mechanism (depicted by arrow 43) and
entry transport mechanism 44 (depicted in Fig. 1, for example, as a hoist), a
first
chamber transport mechanism 45 (depicted in Fig. 1, for example, as a ram/push
device 39 and including an elongated fixed rail assembly 42 (see Fig. lA)), a
transitional transport mechanism 46 (depicted in Fig. 1 as, for example,
another
hoist mechanism), a second transitional transport mechanism 47 (depicted
herein
as, for example, a ram/push device), and a second chamber transport mechanism
48 (depicted as, for example, a roller conveyor). With reference to Fig. IA,
an
2o example of a hoist type entry transport mechanism 44 is depicted, together
with a
representative fixed rail assembly 42 of the first chamber transport mechanism
45.
The entry transport mechanism 44 includes a movable pallet 70 (formed of two
spaced apart lateral rails 71 (one shown) and two, spaced apart transverse
beams
72) and a four cornered support frame 73 supported from above by cabling 74
connected to a drive mechanism (not shown). A hoist type first transition
transport mechanism 46 is of similar construction. The construction and
operation of the depicted integrated transport system 26 is deemed readily
understood by those skilled in the art upon reference to this specification.
Movement of the casting through the various chambers is not limited to those
particular mechanisms depicted herein and alternate transporting mechanisms
will
be apparent to those skilled in the art.
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In a first preferred embodiment, as depicted in Fig. 1, the convection
heating chamber segment 24 is comprised of an upper open air portion through
which the casting moves and is heated and a lower portion formed, for example,
as a hopper (or hoppers) 33 into which falls and is collected (and,
preferably, is
further processed) any sand core materials which may fall from the casting in
this
segment of the heating chamber. In the embodiment of Fig. 1, the convection
segment 24 is shown outfitted with an air re-circulating system 52 which stirs
air
within the convection heating chamber segment 24 to assist in acquiring
temperature uniformity, throughout the convection heating chamber segment
(including at the vicinity of the transitional passage 25), as would be
understood
by those skilled in the art. The herein depicted re-circulating system
includes a
re-circulating fan 53 and related ductwork 54, though other re-circulating
systems
will be readily identified by those skilled in the art. In the embodiment of
Fig. 1,
the convection segment 24 is provided with sand reclaiming features such as
screens 55 and in-hopper fluidization 56. The structure and operation of these
reclaiming features will be understood by reference to the Reference Patents,
especially U.S. 5,294,094 and 5,345,038. In the alternate embodiment of the
combination furnace 10' of Fig. 2, the convection segment 24' includes a
furnace
chamber with a trough 58 with fluidized, migrating bed 59, discharge weir 60,
and
integrated cooling chamber 61 similar to the embodiment of Fig. 1 A of
Reference
Patent U.S. 5,829,509, and the structure and operation of the furnace chamber
segment 24' and related reclaiming will be understood by reference to that
Patent.
The embodiments of Figs. 1 and 2 are also seen as including a weir or spillway
37
by which sand or other particles accumulating within the fluidized bed furnace
is
allowed to spill into the hopper 33 or trough 58, respectively, of the
convection
chamber 24, 24', thus controlling the depth of the bed 27 of the fluidized bed
segment 23, and, preferably, controlling the dwell time of any sand core
particles
within the fluidized bed 27.
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Each of the conduction heating segment 23 and the convection heating
segment 24, 24' of the depicted embodiments will have additional structure and
will operate in a manner all of which will be clearly understood by those
skilled in
the art after review of this entire specification, aided with reference to the
specifications of the "Reference Patents" cited previously herein. As such, no
further description is deemed necessary to enable the functionality mentioned
throughout this specification.
In operation, and in accordance with one preferred method of the present
invention, a casting (not seen), typically laden with outer molds and/or inner
sand
cores (collectively referred to herein as "sand cores") is positioned at the
loading
station 40 ("P 1"). The casting is, for example, carried within a wire basket
or like
transport container 50 which contains the casting yet allows for access to the
casting by the fluidizing medium of the bed 27 and also allows for the
discharge
from the container of sand core material which falls from the casting. The
basket
and casting are moved, for example, by being pushed by the charge transport
mechanism 43 through the temporarily open inlet door 17 to the entry segment
41
(at position "P2"), where the basket rests on, for example, a hoist pallet 70.
The
entry transport mechanism 44 lowers the pallet 70 with the basket 50 and
casting
into the conduction heating chamber segment 23 until the casting is fully
immersed within the fluidized bed 27 and the lateral rails 71 align with the
fixed
rails 42. The fluidized bed 27 is, preferably, comprised of refinery sand
similar in
nature to that sand of which the sand cores of the casting are created.
Preferably,
the fluidized bed has been preheated to an initial temperature prior to
receiving
the casting. The fluidized bed 27 is heated to a temperature sufficient to
perform
the particular casting processing steps desired to be carried out within the
fluidized bed. For example, the bed 27 is heated to a temperature sufficient
enough to conduct heat to the casting of a temperature sufficient to dislodged
sand
core materials from cavities within castings. The core materials preferably
comprise sand that is bound by a thermally degradable material such as, but
not
limited to, an organic resin binder. Thus, in at least the preferred
embodiments,
the fluidized bed is heated to above the combustion temperature of the organic
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NOu - A 2000
resin binder. In preferred embodiments, the processing steps desired to be
performed in the fluidized bed segment 23 are, at least, the process of
removing
sand cores from the casting and the process of reclaiming sand from the core
material which exists in the castings while in the fluidized bed furnace. To
that
end, the techniques of heating the sand core to a sufficiently high
temperature as
well as the techniques of retaining the discharged sand core within the
fluidized
bed 27 for sufficient dwell time to substantially reclaim the sand are
employed as
would be understood by those skilled in the art, especially with reference to
the
"Reference Patents". It is not required that all moldings and sand core be
removed from the casting in the fluidized bed since a certain amount of core
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removal and sand reclamation is provided for and acceptable within the
convection segment 24, though in preferred embodiments a meaningful amount of
core removal and sand reclamation is preferred within the conduction segment
23.
A certain amount of heat treatment of the casting within the fluidized bed
heating
chamber segment 23 is anticipated.
During the time that the casting is immersed within the fluidized bed,
basket 50, with the casting, is moved by the first chamber transport mechanism
45
longitudinally through the conduction heating chamber segment 23 from its
entry
position at "P3" to a final bed position "PF" adjacent the convection heating
chamber segment 24. Various techniques understood in the art are acceptably
used for moving the basket 50 and casting through the fluidized bed,
including,
for example, the ram/push device 39 and rail assembly 42 depicted. The push
device 39, in the exemplary embodiments, pushes the basket 50 laterally off
the
rails 71 of the movable pallet 70 onto the fixed rails 42, through the
fluidized bed
chamber segment 23, to a resting position on the rails 71 a of the movable
pallet
70a of the first transitional transport mechanism 46 (position PF). From
position
PF, the movable pallet 70a, with the basket 50 and casting, is raised by the
transitional transport mechanism 46 (for example, by a hoist) through the
transitional passage 25 to a position in the convection heating chamber
segment
24 adjacent the second chamber transport mechanism 48. From this position the
basket 50 is moved longitudinally off the pallet rails 71a and then through
the
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convection heating chamber segment 24, first by the second transitional
transport
mechanism 47 and then by the second chamber transport mechanism 48. Again,
movement of the casting through the various chambers is not limited to those
particular mechanisms depicted herein and alternate transporting mechanisms
will
be apparent to those skilled in the art. For example, in one embodiment (not
shown) the casting is acceptably transported through the entire chamber 14 by
a
basket supported overhead by a cable extending from a shuttle moving
longitudinally over the frame structure 12 on an overhead rail. The shuttle
selectively spools and unspools the cable to raise and lower the basket at
appropriate times.
It is the intention of the present invention that heat generated in the
conduction heating chamber segment 23 will pass freely through the
transitional
passage 25 into the convection heating chamber segment 24 and, thereby,
provide
preheat to the convection segment and assist in effecting a continuing casting
heating process from the conduction heating environment to the convection
heating environment without meaningful change in temperature. As the casting
is
moved through the convection heating chamber segment 24, the chamber segment
is heated to sufficient temperature to perform the casting processing steps
desired
for this chamber segment. For example, preferably, heat treatment of the
casting
is performed and completed during the casting's containment within the
convection heating chamber segment 24.
Simultaneously with the heat treating, it is desired that any remaining sand
core is removed from the casting and the sand is substantially reclaimed from
the
remaining sand core portions. Accordingly, for assisting in removal of any
remaining sand of the core of the casting, hot air can be directed toward the
casting in one or more directions so as to bombard the casting on different
sides
as the casting is moved through the convection heating chamber segment to
remove any remaining sand out of the casting. Alternatively or in conjunction
with the application of hot air against the casting, the casting further can
be
quenched by directing air toward the casting in one or more directions. This
quenching air tends to cool down the casting and force any remaining sand of
the
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~
core out of the casting. Any sand that is removed from the casting in such a
manner will tend to fall through the second chamber transport mechanism 48 for
collection by the reclaiming sand hoppers 33. Further, as the casting is moved
through convection heating chamber segment 24 toward the exit portal 18, the
castings can further be subjected to a vibrating mechanism or other similar
mechanism that vibrates or shakes the castings to fiuther assist in the
removal of
any remaining sand from the castings. Any remaining sand removed or vibrated
out of the castings will be collected in the reclaiming sand hoppers 33 for
reclamation and discharge. It is possible that any of these steps of applying
hot
air, applying cool air to quench the casting, and/or vibrating the casting as
it is
moved through the convection heating chamber segment 24 can be used
separately or in conjunction with the heating and reclamation process of the
invention to further assist in removal of any remaining sand of the sand core
from
the castings. Upon completion of the appropriate processing, the basket and
casting are conveyed out of the exit portal 18.
Fig. 3 depicts a third embodiment of the combination fumace 10" which
does not include a hopper or a trough for retention of fallen sand core
materials
but, rather, includes a sand return 62 by which sand core collected in the
convection heating segment 24" is conveyed back to the fluidized bed segment
23
where it is further processed for reclaiming of sand. A discharge weir 64
within
the fluidized bed segment 23" is provided in order to discharge reclaimed sand
from the fluidized bed segment, and the depth of the bed 27 is established or
regulated to provide proper dwell time for reclamation. The weir 64 acceptably
discharges to a cooling chamber 61' as will be understood by reference to the
embodiment of Fig. 113 of the 5,829,509 patent.
In accordance with the most preferred methods of the present invention,
the combination furnace 10 is utilized to perform the three-in-one processes
of
casting processing known as core removal, in furnace sand reclamation, and
heat
treatment. However, it should be understood that the combination furnace 10 of
the present invention is acceptably utilized to perform one or more of the
mentioned processes or other processes associated with the processing of
castings
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using heat. In alternate embodiments where it is planned that no core removal
will take place within the combination furnace (for example, when all sand
core
molds are removed, perhaps by vibration techniques, prior to delivery of the
casting to the furnace), then the sand reclaiming features of the furnace,
such as,
the spillway 37, screens 55, and fluidizers 56 are acceptably removed.
The present invention is seen as relating to the integration of a plurality of
(two or more) heating environments in such a manner as to effect a continuous
heating chamber, and, in accordatice with the present invention, at least two
1o adjacent heating environments within the continuous heating chamber are
distinct
from one another. In the herein described embodiment, the distinct
environments
are disclosed as one being a fluidized bed conduction furnace and the other a
convection furnace.
It is clear and understood that the combination heating environment
expressed in Figs. 1-3 herein is acceptably two segments of a larger heating
chamber comprised of other heating chamber segments, including other heating
environments. Such an expanded heating chamber 14', 14" is schematically
represented in Figs. 4 and 6. For example, in one alternate embodiment (see
Fig.
6), another segment 80 comprising a fluidized bed furnace type of heating
2o environment follows the convection segment 24 of Fig. 1. Following the
spirit of
the present invention, in such embodiment, a heat channeling transitional zone
81
is provided between the convection segment 24 and the additional conduction
heating chamber segment 80 of Fig. 6.
By way of further example, in another embodiment (not specifically
shown, but inferentially seen in Fig. 4), a convection type heating segment is
added to the front of the fluidized bed conduction segment 23 of Fig. 1, with
a
heat channeling transitional zone in between. In still other embodiments (not
shown), a duplicate of the combination fluidized bed and convection system of
Fig. 1 is "piggy-backed" to the front or back (or both) of the system shown in
Fig.
1. In such latter embodiments, the invention again includes a heat channeling
transitional zone provided between each adjacent heating environment segment.
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Furthermore, the present invention is not limited by the order of the
respective heating environments. Rather, for example (as schematically
represented by Fig. 5), should a particular processing technique favor the
placement of a convection heating environment prior to a fluidized bed
conduction environment, then the order of the heating environments as shown in
Fig. 1 is acceptably reversed. Fig. 5 schematically shows a convection heating
environment as the first heating segment 23"' and a fluidized bed conduction
environment as the second heating segment 24"'.
As illustrated in Fig. 7, in a further alternative embodiment of the second,
1o convection heating segment 24"", a rotating mechanism 80 is provided along
the
second chamber transport mechanism 48"", positioned at an intermediate point
along the length of the second heating chamber segment 24"". The rotating
mechanism can comprise a pair of pivoting rails, such as indicated by dashed
lines
81, or similar mechanism to engage and lift the castings, so as to cause the
castings to be reoriented on the transport mechanism 48"" as illustrated in
Fig. 7.
The reorienting of the casting on the transport mechanism helps to enable a
higher
percentage of sand to be dislodged or shaken loose and thus removed from the
castings so as to be collected in the sand reclamation hoppers. The rotating
mechanism 80 can further be used separately or in conjunction with a further
application of hot air or cooling air being directed against the castings from
one or
more directions in order to heat or quench the castings to further assist in
the
removal of sand from castings, or in conjunction with the vibrating mechanism,
as
discussed above, so as to further insure a substantially complete removal of
sand
from the sand cores from within the castings.
Whereas the disclosed embodiments have been explained using the
fluidized bed conduction heating environment and the convection furnace
heating
environment as adjacent heating environments, it is clearly within the scope
of the
invention to incorporate any distinct heating environments as the at least two
adjacent distinct heating environments. Such heating environments might
acceptably include any heating environment known and understood currently or
in
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the future by those skilled in the art, including, without limitation,
conduction,
convection, and radiant heating environments.
While the embodiments which have been disclosed herein are the
preferred forms, other embodiments will suggest themselves to persons skilled
in
the art in view of this disclosure and without departing from the spirit and
scope
of the claims.
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